Telegraph signal repeater



Patented July 12, 193s UNITED srl-tres PATENT OFFICE TELEGRAPH SIGNALREPEATER Application August 30,

13 Claims.

t inactive relay from being operated by line discharges when used withlong cable line circuits.

Another object is to provide a repeater of simple design which may beeffectively operated in conjunction with any one of a plurality oi linesof greatly diiering characteristics.

Another object is to simplify the switching of repeaters of this type byan arrangement of the parts such that the adjustment oi the repeater foroperation with lines of different characteristics is confined to asingle instrumentality, such as a resistance for adjusting the linecurrent.

The present day tendency is to interconnect telegraph subscribersthrough switchboards which are equipped with repeaters which areindividual to the lines or loops and with other repeaters, such as cordcircuit repeaters, which must be adapted for use with lines of greatlydiffering characteristics. The tendency is, furthermore, to use longerand longer subscribers loop cir cuits and to include the conductors forsuch loops in cables, so that their capacity to ground becomes quiteappreciable. The tendency is, furthermore, toward Ahigher speed oftransmission.

For these reasons, it is important that repeaters should require as few.adjustments as possible for their proper operation with lines ofdifferent characteristics. This is, of course, essential particularlywith cord circuit repeaters, which may be connected to long cable lines0r to open wire lines, but it is also important in connection withrepeaters permanently associated with their loops in order to eliminatethe continual balance adjustments which hitherto have been necessary ininterconnecting subscribers loops.

It is also important that the tendency of line discharges to kick-ofithe inactive relay be obviated and, whereas various ways ofaccomplishing this object have already been proposed, the generalobjection to those arrangements is that they ordinarily affect the biasand introduce distortion of the signals.

In accordance with a feature of the invention, the sending relay of atelegraph repeater is connected to transmit directly into the line sideof the outgoing circuit and the inactive receiving relay has its linewinding connected to the return side of the outgoing circuit, therebyprac- 1935, Serial No. 38,526

tically entirely preventing the line discharges from passing through theinactive relay and eliminating the insertion of anti-kick-of circuitelements.

In accordance with another feature of the in* vention, phase equalizingmeans are provided in connection with one or the other, or both, of theline and secondary windings of the receiving reu lay. The object of thisis to compensate for delay of the impulses through the line winding dueto their passage over both sides of the line circuit in series and thusprevent the receiving relay from operating during sending. 'Ihe elementsof the phase-equalizing means may be standardized and may be givensuitable values for any line circuits which may be encountered incommercial operation. This phase equalizing means may be in the form ofa resistance capaci tance network for advancing the phase of outgoingimpulses through the line winding of the receiving relay; or in the formof an inductance for retarding the impulses through the balancingwinding of the receiving relay; or it may combine both of thesearrangements.

In accordance with still a further feature of the invention, a variableline current control impedance is inserted in the line side of the linecircuit and the balancing network is reduced to consist only of a fixedresistance of a value suitable for all line circuits which may beencountered in commercial operations.

The invention will now be described in connection with the attacheddrawing which shows diagrammatically a circuit arrangement for atelegraph signal repeater embodying the various features of theinvention. Only so much of the repeater circuit is shown as is directlyassociated with a line or loop leading to the distant subscribersstation.

The repeater station Ris connected over a pair line which consequentlywill `have mutual disl,

tributed capacity, represented by condensers H4 and l5, and which willhave distributed capacities towardthe cable sheath which is grounded,which capacities are represented by condensers ||0, ||2 and ||3.

The repeater station R comprises a transmitting relay which may beoperated in any desirable manner either from a local source or from adistant station which may be similar to the station S. Relay |0| has itsarmature connected directly to the outgoing line conductor |08 and inits marking and spacing positions applies alternately positive andnegative potential, respectively, to that conductor. The receiving relay|02 has its armature and contacts connected in any desirable manner forrepeating signals into a local circuit or into a line circuit similar tothe line |08 and |09. Relay |02 has a line winding connected from thesource of negative potential to the return conductor |l9 for receptionof signals from station S. This relay also has a second or balancingwinding connected from the armature of relay |0| through balancingresistance 01 to ground.

With the circuit in normal position as shown in the drawing, currentfrom the source of positive potential is supplied over marking contactof relay |0| directly to conductor |08 maintaining a positive charge onCondensers IIE! and lll, the current continues through the subscribersstation S over conductor |09 through the line winding of relay |02 tonegative potential. The condensers ||2 and 3 consequently are normallycharged to a negative potential. Condensers Il!! and I| 5 will normallybe charged between the positive and negative potentials applied to thetwo line conductors.

Another circuit may be traced from positive potential over the markingcontact of relay |0| through the biasing winding of relay 02 andresistance |07 to ground. The current through the first circuit, andthus in the line winding of relay |02, is in a direction to hold therelay in marking position and is approximately twice the current in thesecond circuit through the biasing Winding of relay |02, which is in adirection to tend to operate the relay 02 to its spacing position. Whenthe line circuit is opened at subscribers station S for transmission ofsignals to the repeater station the line circuit including line windingof relay |02 becomes currentless. Relay |02 consequently responds byoperating to spacing for the duration of the opening of the linecircuit. During such a spacing impulse the charges on line Condensers||0, HI, H2, H3, H4 and H5 remain practically unaltered.

Again assuming normal condition of the circuit and that a spacing signalis to be transmitted by operation of relay I0! to its spacing contact,negative or spacing potential will then be applied directly to conductor|08. The subscribers station consequently will be practicallycurrentless and thus responds to the spacing impulse, and both lineconductors will be connected to spacing potential. The condensers |52and ||3 consequently remain practically unalected, whereas the charge onCondensers H0 and will be reversed, with the result that very littlecharging current will flow through the line winding |02 over conductor|09 due to the grounded capacities, and that a comparatively heavycharging current will flow over the line conductor |08. The charges onCondensers IM and H5 will be reduced to Zero, and this small surge willappear in both line conductors, however without appreciable eiect on therelay |02 or the receiving equipment at substation S. With relay |0| inspacing position negative potential is also applied to the biasingwinding of relay |02 in a direction the reverse of the previouscondition and relay |02 remains in marking position during the spacingimpulse. When relay |0| returns to its marking position the charges onCondensers H0 and Ill will again be reversed and current will again flowthrough the subscribers station, which thus responds to the markingimpulse. The mutual capacities |54 and ||5 will again be charged up tonearly full line potential, but this surge is too small to appreciablyaiect relay |02. Current will also flow in the line winding of relay |02and the opposing current in the biasing winding will be reestablished.Thus relay |02 will respond to impulses produced by opening of the lineat the subscribers station, but will not respond to impulses produced byreversing the potentials to the line circuit by transmitting relay |0.

From this description it is clear that the comparatively large currentsurges due to the ground capacity of the line conductors |03 and |09 donot aiect receiving relay |02,

In order that a repeater of this type may be used with diiierent lines,it is necessary to provide means for adjusting the line current. Forthis purpose variable resistance |03 is inserted in the outgoing lineconductor |08. With the line winding of relay |02 in the other conductorthe presence of resistance |03 in the outgoing conductor will not delaythe decay of current through the line winding of relay |02 when aspacing signal is transmitted from the subscribers station and thus willcause very little distortion.

Inasmuch as relay |02 is practically unaffected by the static conditionson the line circuit it is evident that the articial line |07 need not bearranged to balance such static condition; it may therefore be made of asimple resistance of a value which may be suitable for nearly all loopcircuits that may be encountered in commercial plants.

In view of the fact that the line impulses from the contacts of relaylei must rst pass through the line circuit and the distant subscriberstation before they reach the line winding of relay |02, the impulsesthrough the local circuit including the balancing winding of relay |02will reach the biasing winding before the line impulses reach the linewinding. Whereas this is satisfactory when relay IGI operates tospacing, the reversal of the current in the biasing winding of relay |02before a marking impulse arrives in the line winding may cause the relayto kick-off.

This phase relation may be compensated for in dierent ways; thus bymeans of a capacitance network |0E connected across the outgoing line amarking impulse may quickly be transmitted to the line winding of. therelay |02 and thus prevent the biasing winding from operating the relayto spacing. A similar eiect may be obtained by introducing inductance|05 in the local circuit for the biasing winding of relay |02 therebydelaying the arrival of a reverse impulse through that biasing windingsuiiiccntly to permit the marking impulse to arrive iirst in the linewinding of relay |02. It is of course possible to use both of thesearrangements simultaneously as shown in the drawing. It will, however,be found that a network comprising a single resistance and capacitancebridge |06 will be suflicient; a capacity of 2 microfarads in serieswith an 3,000 ohm resistance has been found to give satisfactory averageoperation. In some cases it may be desirable to add a similarresistance-capacitance bridge of a diierent time constant for thepurpose of improving the wave shape.

It has been found that the phase correcting means have no distortingeffect upon the signals in either direction and the system has theadvantage of not requiring devices for preventing kickoff inserted inthe line circuit proper, which devices will usually have the effect ofintroducing bias.

It may be noted that the mutual distributed capacity between conductors|08 and |09 represented by condensers ||4 and ||5 would aid incorrecting the phase relation between the irnpulses through the twowindings of relay |02.

From the description given above it is apparent that all parts of therepeater circuit may be standardized for permanent use with any linecircuit that may be encountered in a commercial plant or for use as acord circuit repeater for connection with any type of line circuit. Theonly adjustable device in this arrangement is the line resistance |03.It is thus possible to standardize the equipment to a high degree andalso to obtain the necessary flexibility for switchboard operation.

For a complete system extending from the subscribers station S toanother similar subscribers station the entire system shown in thedrawing, except relays |0| and |02, may be duplicated. Contacts S and Mof relay |02 would constitute sending contacts for the other linecircuit corresponding to the contacts of relay lill; one winding ofrelay |0| would be connected to the incoming line and the other windingwould be included in a biasing circuit similar to that including thelower Winding of relay |02 and resistance What is claimed is:

1. A two-wire circuit having capacity to ground and having a line sideand a return side, signal transmitting means connected to said line sideAfor charging said line side alternately to two different potentialswith respect to ground, polar receiving relay means having a winding,and a source of potential permanently connected through said windingvtosaid return side.

2. A telegraph signal repeater operating into an outgoing two-wire linecircuit having capacitance to ground, comprising a transmitting relayhaving contacts for applying alternate potentials to one wire of saidline circuit, a receiving relay having an operating winding, a source ofpotential equal to one of. said alternate potentials connected throughsaid winding to the other wire of said line circuit.

3. A two-wire circuit having capacity to ground and having a line sideand a return side, signal repeating means comprising transmitting meansconnected to said line side for charging said line side alternately topositive and negative potentials with respect to ground, a iixedpotential connected to said return side, and a polar receiving relayhaving a winding connected in said return side to be substantiallyunaffected by charging currents to ground in said two-wire circuitduring operation of said transmitting means.

4. A telegraph signaling system including a polar relay having a linewinding and a secondary winding, and signal transmitting means forsending signal impulses through both of said wind-v ings, and a two-wireline circuit including a remote receiving equipment, both wires of saidline circuit being connected to a point between said transmitting meansand said line winding.

5. A telegraph signaling system in accordance with claim 2 in which saidline circuit is serially connected between said transmitting means andsaid line winding.

6. A long two-wire line circuit, signal transmitting means including asource of signaling potential at one end of said line circuit, receivingequipment at the other end of said line circuit, a polar relay at saidone end of the line circuit having one winding connected over the twowires in series of said line circuit to said transmitting means andhaving another winding connected through a local circuit to saidtransmitting means.

'7. A telegraph signal repeater operating into an outgoing line circuitand comprising a transmitting relay having contacts, a receiving relayhaving a line winding and a second winding, a balancing circuitconnected through said second winding to said contacts, said contactsbeing connected to the line side of the outgoing line circuit,

l and said line winding being connected to the return side of. theoutgoing line circuit.

8. In a differential telegraph repeater, transmitting contacts connectedto the line side of an outgoing circuit, a receiving polar relay havinga line winding connected to the return side of said outgoing circuit,and a second winding connected in a balancing circuit from saidcontacts, circuit means connected to one of said windings tosubstantially equalize the phase relation of impulses in said windingstransmitted by said contacts.

9. A differential telegraph repeater in accordance with claim 8 having asole regulating means for adjusting said repeater for differentoperating conditions consisting of an adjustable impedance connected tosaid line side.

l0. A differential telegraph repeater system comprising a polarreceiving relay having a line winding and a second winding, signaltransmitting means, a balancing circuit connected through said secondwinding to said transmitting means, a phase controlling networkconnected between said line winding and said transmitting means,

and a two-wire outgoing line circuit connected across said network.

1l. A repeater in accordance with claim 7 further comprising a phasecorrecting capacitance connected in a local circuit between saidcontacts and said line winding, and a variable resistance connectedbetween said contacts and said line side for adjustment of the linecurrent.

l2. A long two-wire line circuit having capacity to ground, transmittingmeans connected to the line side at one end of said two-wire circuit,receiving relay means having a winding connected in the return side atsaid one end of. said twowire circuit, a balancing circuit to preventsaid relay from responding to the operation, of said transmitting meansincluding current regulating and phase correcting means connected tosaid line winding and a balancing winding on said relay connected tosaid transmitting means.

13. The combination in accordance with claim 6 further comprisingcapacitance circuit means in series with said one winding and connectedin multiple to said line circuit and inductive circuit meansV in serieswith said other winding.

WALTER W. CRAMER.

